A revised application to test the hypothesis that tumorigenesis in Wilms tumor results from mutations, either germline or somatic, at more than one locus in the tumor cell. One Wilms tumor gene is known: the transcription factor WT1 on chromosome 11p. The PI proposes to fine map a second locus, WT2, for hereditary Wilms tumor on chr19q and identify the responsible gene. Specific Aims are: (1) Ascertain and sample additional families with familial WT; (2) identify the subset that show linkage to 19q (as well as any families linked to other regions implicated in WT); (3) explore all familial cases, whether linked to 19q or not, for LOH involving the critical region on 19q or other regions implicated in WT; (4) refine the position of the 19q WT2 locus on a physical map of the region using meiotic recombination, loss of heterozygosity, and disequilibrium approaches; and (5) screen candidate genes and ESTs in the region for germline and somatic mutations in WT patients